Cutter



Feb. 23, 1932. J, IBREUER 1,847,054

CUTTER Filed May 2, 1929 llllll llllll-l Hill 1! mm: 7

lNVENTO John P reuer ATTORNEYS Patented Feb. 23,

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The present invention relates generally to improvements in rotary cutters, and particularl gear cuttin hobs. The general 0 jects of the present invention reside in the provision of a new and improved hob which has a higher-cutting efficlency, a greater cuttin clearance, a longer life, and distribution 0 wear over a larger surface than hobs provided heretofore.

Another object resides in. the provision of a novel hob in which the teeth are inclined' laterally about the radial center of the face out of the thread helix to tional, clearance on one si e, and in which material is removed from the teeth to proviie the necessa ry clearance on the other s1 e. t

A more specific object'resides in the provision of a hob of the fore character in which an additional'to re of is provided to compensate for the ditional side clearances so that the faces of'the teeth can be resharpened without altering the effective cuttin contour.

An important object resides in the provision of a novel hob in which the teeth are inclined laterally so as to shorten the lead of each individual tooth, and in which the teeth also have a reduced pressure angle.

Another object is .to provide a hob of the foregoing character in which the upper side ed es of the teeth arerounded.

urther objects and advantages will become a parent as the description proceeds. In t e accompanying drawings, Figure 1 is an elevational view of a hob havmg a single right hand thread embodying the eaturesof my invention.

ting Figure2is a fragmentary end elevational view of the hob.

Figure 3 is a diagrammatic view in cross section showing a portion of the hob in cutengagement with a portion of the gear F 4' fra ts f 1 .188. en rypanviewo twlggib c essive hob 1 two aterally adjacent hob teeth.

While the invention is susceptibleofvarious modifications\ and alternative construcrovide an addior eft hand e 5 is a transverse sectional yiew of 1839. Serial lie, '89,?!

tions I have shown in the drawings and will herein describe in detail the preferred embodiment, but it is to be understoodthat I do not thereby intend to limit the invention to the specific fdrm disclosed, but intend to cover allmodifications and alternative constructions falling within the spirit and scope of the invention as expressed in the p appended claims. I

. Referrin more particularly to the drawings, theho constituting the exemplary embodiment of the invention comprises a body 10 adapted to be mounted on a supporting arbor (not shown). The perirlrheral surface of the body is formed with a p urality of hob teeth 11. In common hob practice, the hob. teeth ma be arranged in one or more right hand elical threads interrupted by generally longitudinal straight or inclined gashes. In the present instance, I have shown the teeth 11 generally arranged in 'a single right hand helical thread intersected by a pluralitg of straight lon 'tudinal, ashes 12, althoug it is to be un erstood' t at in its broadest concept, the invention is not limited to such construction.

Each tooth 11 has a front face 13 defining glcigtng contour a back 14 3ee. yamar 'e-g ,atop15 efined by a marglfib-c- -g, a dra side 16 defined by a margin 0- --f, an a shear side 17 defined by a margin c ig- It is common practice to arrange the hob teeth throughout their length in a true helical thread having a lead corresponding to the normal circular pitch of the. gear to be hobbed, andto providethe teeth with a uniform eccentric relief. The thread helix is represented by dotted lines 18 in Figs. 1 and 4. I have observed that wear on the teeth first becomes pronounced on the entering side (shear side 17 of the cuttin contour ab c -d near the top, next .on t e outer corners b and a, side 16) near-the top. Thus, the top of the cutting contour b-c, although it is relatively small inextent, does most of the cut- I ting and is subjected to most of the wear. I

The first wear is caused by rubbing on'the and then on the leaving side (drag.

perature, thereby substantially reducing the resistance to wear of the cutting face. To avoid excessive wear on the sides of the teeth 11, and incidentally to decrease the drivm power required and to increase the rate 0 production, I provide additional side clearance. This clearance may be provided on either or both sides of the teeth, and may be formed in any suitable manner. In the present instance, I tilt each tooth 11, about the radial center line of the front face 13, out of the hob helix. Preferably the tooth 11 is tilted to the right as viewed from the front face, i. e., is tilted toward the shear side 17, thereby providing clearance on the drag side 16. The direction of the. tilted teeth is represented in Fig. 4 by the lines 19. Side clearance is then cut on the shear side to bring same within the limits of tolerance, and preferably still more to increase the clearance. To this end, the material is removed to the plane odz'-j (see Fig. 4). As a result of the additional side clearances, a sharply defined cutting contour is produced, and the cutting efliciency is greatly increased. No excessive rubbing and wearing takes place on the sides of the teeth.

Providing additional side clearance tends to decrease the width of the teeth from front to rear. This usually is immaterial in a rou hing hob. In a finishing hob, it is desira le to provide a tooth form which will retain a predetermined cutting contour upon resharpening, and hence to compensate for the additional side clearance, an additional top clearance is provided. This top clearance is in excess of the normal eccentric relief, and is such that the width of the top from front to rear is uniform.

Most of the cutting in a hobbing operation is done by the outer end of the tooth. Yet

this partof the tooth is relatively small in effective area, and hence most subject to wear. An im ortant feature of the present invention resi es in the provision of a hob in which the teeth are not onl inclined out of the thread helix and provi ed with additional side clearance, but in which also the face of each tooth is wider at and near thetop than heretofore so that heat and wear 1 will be distributed over a wider area. This is accomplished by shortening the lead of the hob. As a result, the pressure angle of the hob is reduced. Heretofore, the hob and the gear being hobbed have had the same pressure angle, for example 20, indicated at 0 in Fig. 3. The present hob has a pressure angle less than that of the gear to be hobbed, for example 16, indicated at bin Fig. 3. The change in pressure angle results in a more vertical disposition of the sides 16 and 17 of the teeth, thereby widening the top bc and narrowing the root ad of each tooth. The new form will however generate the same illustration, the former may include an angle of 32, whereas the latter may include an angle of 40. Asa result, the teeth 11 are narrower at the base and wider at the ends than the standard teeth, thereby increasing the area most exposed to wear. The ar Ipitiih line is represented by the line 20. e

base circle 21, and is represented bythe line 22. The pressure a'ngle 4 of the teeth 11 is substantially less than the pressure angle 0 of the standard teeth.

In finishing hobs, the top edges b-f and c-g of the teeth 11 are quite-sharply defined, but preferably are slightly rounded, for example on a radius of one-tenth of the thickness of the tooth measured at the itch line. In roughing hobs, the to edges 0 the teeth 11 are rounded very su tially as illustrated in Fig. 5.

I claim as my invention:

1. A hob having a plurality of Gil-:3? teeth arran ed in a peri heralhelical t said teeth aving a need mum angle, each of said teeth being la y inclined out pitch line does not coincide with the .line 20, but falls between the line 20 and the of the thread helix about the medial line of the front face.

2. A hob having a plurality of cu teeth arranged in a peripheral helical threa each of said teeth laterally inclined out of the thread helix a ut the medial line of the front face to provide a substantial cuttin clearance on one side, having a cutting c earance on the other side sufiicient to compensate for the inclination, and having a relief suflicient to produce a top surface mu 0 rm in width throughout its length.

3. A hob having a plurality of cuttin teeth arranged in a peri 'heral helical threiuf said teeth having a need pressure angle, each of said teeth beinglaterall y inclined Ill out of the thread helix toward the shear side I about the medial line of the front face to provide a substantial cutting clearance on the drag side, and having a cutting clearance on the shear side suflicient in magnitude to compensate for the inclination.

4. A'hob having a plurality of cuttirfi teeth arranged in a peripheral heli thread, said teeth having a reduced presure angle each of said teeth laterall inclmed out of the thread hehx tower the shear side about the medial line of the front face to provide a substantial cutting clear-- ance on the drag side, havin a cutting clearance on the shear side su cient in magnitude to compensate for the inclination, and having a top relief suflicient in magnitude to produce a top surface uniform in width throu hout its'length.

5. hob having a plurality of cutting teeth arranged in a peripheral helical thread, said teeth having a reduced pressure angle, each of said teeth bein laterally inclined out of the thread helix a out, the medial line of the front face, the side edges of the top being rounded.

6. A hob having a plurality of cutting teeth arranged in a peri heral helical thread, said teeth having a re uced pressure angle, each of said teeth being laterally inclined out of the thread helix toward the shear side aboutthe medial line of the front face to provide a substantial cutting clearance on the drag side, having a cutting clearance on the shear side sufficient in magnitude to compensate for the inclination and having a top relief sufiicient in magnitude to produce a top surface uniform in width throu hout its length, the side edges of the top bemg rounded.

In testimony whereof, I have hereunto afiixed my signature. JOHN P. BREUER. 

